Controlled release of chemicals in oilfield operations

Abstract

Particulates, such as proppants, that are coated with a coating agent selected from the group consisting of: organosilanes, organosiloxanes, polysiloxanes, long carbon chain hydrocarbon amines containing no silicon or fluoro-based groups in the molecule, amine functionalized polyolefins and polymerizable natural oils; and a chemical additive selected from the group consisting of: a scale inhibitor, a biocide, and an H2S scavenger. The coating agent controls the release of the additive from the particulate surface into surrounding fluid, providing a slow release that promotes the long lasting effect of the additive. The coated particulates have use in oilfield applications such as hydraulic fracturing operations, gravel pack operations, and in water treatment processes.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. provisional application 62 / 326,642, filed Apr. 22, 2016, the entirety of which is incorporated herein by reference.FIELD[0002]Compositions and methods for different applications, particularly oilfield operations such as hydraulic fracturing. More particularly, this disclosure relates to the embedment or attachment of oilfield chemicals, such as scale inhibitors and biocides, to a particulate coating, to control their release into a surrounding fluid.BACKGROUND[0003]Hydraulic fracturing is a technology commonly used to enhance oil and gas production from a subterranean formation. During this operation, a fracturing fluid is injected along a wellbore into a subterranean formation at a pressure sufficient to initiate fractures in the formation. Following fracture initiation, particulates, commonly known as proppants, are transported into the fractures as a slurry, that is, as a mixture of proppants...

AI Technical Summary

Benefits of technology

The patent describes a way to attach chemical additives to small particles, so that they can slowly release from the surface and influence the surrounding fluid. This slow release can have a long-lasting effect, and is useful in various oilfield operations and water treatment processes. The coating agent used on the particles delays or prolongs the release of the chemical additive compared to uncoated particles, and this can be important in determining the overall effect of the additive.

Problems solved by technology

In comparison with a fluid having a cross-linked gel, fluids comprising linear gels, i.e., fluids containing enough polymer to significantly increase fluid viscosity without cross-linking, cause less formation damage and are more cost-effective, but they have relatively poor suspension capability compared to fluids having a cross-linked gel.

The formation of scale, be it organic or inorganic, often occurs in both the subterranean formation and in the wellbore, and impedes production flow and worsens pipe corrosion.

Another common problem during production is the growth of sulfate reducing bacteria (SRB), which causes well souring, i.e., an otherwise clean well starts to produce hydrogen sulfide (H2S).

SRB are a kind of bacteria that consume sulphates in the fluids and convert them to H2S, which is a very toxic and pungent gas that causes problems in both upstream and downstream processes.

Unfortunately, most of these compounds will flow back with the fracturing fluid, after the fracturing treatment.

One of the potential drawbacks of the '291 patent teaching is that ceramic proppants are very expensive compared to sand proppants and they only find limited applications in formations deeper than 4,000 meters, which excludes current shale formations.

Its drawback is that adding extra small particles, such as clay, into the formation may reduce conductivity of the proppant pack, which is vital for well production.

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